The subject invention concerns a method for laser-optical navigation and a device for performing the method.
Within farming and forestry there is a need for devices which would make the use of utility vehicles and implements easier by providing automatic and accurate control and guidance of the position of the vehicles and implements during driving and operation thereof. If such position control and guidance were obtained, the operator of the farming or forestry equipment could devote his attention more fully to other aspects of the work, such as regulating and control of the operation of the utility implements and the results of the work, whether it be manure-spreading, sowing or harvesting. In addition, it is usually very tiring for the vehicle operator to drive for instance a tractor on a field for any length of time with absolute accuracy along a line which should be as straight as possible despite the uneven ground, such as is required for instance for manure-spreading and fertilizer-spreading, sowing or harvesting operations.
A number of different navigation systems have been developed, all having for their purpose to continuously determine the position of a moving object, such as a vehicle. Several of these systems operate on radio position finding technology and they are best suited for navigation operations that are intended to cover large open areas or when the distances between the transmitter and the receiver units are large or comparatively large. For this reason they are used mainly onboard ships at sea or in aeroplanes. Various types of radio finding systems, for instance satellite based systems, are useful on offshore installations to determine the position of oil rigs and accommodation platforms. However, for navigation purposes within limited areas, such as a field having a surface area of about a few acres, such systems are not particularly useful, for the reason that because of the "crowdedness of the ether medium" it is not possible (or allowed) to utilize the broad wavebands as would be desirable if one wants to achieve the high position-determination precision aimed at, i.e. within a fraction of a meter. Radio navigation on the basis of a narrow waveband, on the other hand, requires complicated, and therefore expensive, transmitter and receiver equipment. Also other factors, such as reflection errors and interference, restrict the usefulness of radio navigation systems for position determination purposes which must meet the accuracy requirements set forth above. These systems therefore are used primarily within ranges of a few hundred kilometers and the most sophisticated systems of this kind may achieve an accuracy of about a meter across water and about ten meters across land.
Navigation systems operating on microwave technology also exist. Experimentally, microwave technology has been used for navigation purposes also within more limited areas, such as is the case within agriculture and forestry. However, this technology requires comparatively expensive and complex equipment and thus for that reason alone its use is limited.
Neither radio nor microwave navigation systems provide accurate attitude determination, which is a prerequisite if exact control and guidance of soil working implements and control of unmanned vehicles are to be achieved.
The purpose of the invention is to provide practical and reliable navigation equipment in which laser-optical systems are used. Prior-art laser-optical systems have hitherto been used only indoors for vehicles which move across level ground within a very limited area. Consequently, such prior-art systems cannot in any respect meet the demands that necessarily must be made on equipment intended to be used on a vehicle which is driven on uneven surfaces, such as a field, for instance.